1. Field of the Invention
This invention relates to a process for producing a monomolecular built-up film of the chemisorption type which has been developed for use as functional electronic devices such as molecular elements.
2. Description of the Prior Art
For the deposition of monomolecular layers, there is typically known a method of producing Langmuir-Blodgett (LB) built-up films. In this method, amphiphilic substances or amphiphiles having both a hydrophobic group and a hydrophilic group and dissolved in organic solvents are spread on a water surface and gathered to form a monomolecular layer, followed by evaporation of the solvent. The molecules on the water surface are gathered by means of a barrier or barriers. In this state, a substrate is vertically moved with respect to the resultant monomolecular layer while adding a given surface pressure. This is repeated to build up a plurality of monomolecular layers on the substrate.
The LB method is considered as one of promising methods of enabling one to construct layered structures in the recent development of molecular devices wherein specific functions are imparted to molecules. According to the LB method, a monomolecular layer having a thickness in the order of several tens angstroms can be formed. Built-up films of the layers are readily obtained. However, the monomolecular layers in the built-up film are not chemically bonded with one another, resulting in unsatable characteristic properties. In addition, the film obtained by the LB method is not so good with respect to the density of the molecules with an attendant problem that defects such as pinholes are involved in great number.
The built-up film formed according to the LB method is not considered to show its inherent properties to a full extent.
J. Sagiv proposed in U.S. Pat. No. 4,539,061 a process wherein a monolayer is formed on a substrate by chemisorption and is chemically modified on the entire surface thereof by the use of reagents. Another monolayer is built up on the entire surface of the previously formed monolayer. The desired number of monolayers is formed by repeating the chemisorption and chemical modification. In this process, however, selective formation of monomolecular layers one on the other with good bonding is not shown. Thus, it is not possible to build up a monolayer selectively at the same interface.